The present invention relates to a TCP semiconductor device using solder resist having appropriate flexibility and a liquid crystal panel display using such a device, and also concerns a testing method for disconnection of the wiring pattern thereof.
The TCP (Tape Carrier Package) semiconductor device having a flexible bending property is referred to as a flex TCP semiconductor device. The flex TCP semiconductor device is used as a package for driver semiconductors especially in a liquid crystal panel which has a small frame portion.
Recently, there has been a strong trend toward large-size liquid crystal panels, and at present, those panels exceeding 13 inches have been produced for use in notebook PCs (Personal Computers). Therefore, there are ever-increasing demands for the development of flex TCP semiconductor devices used for large-size liquid crystal panels.
FIG. 7(a) is a plan view that shows a schematic construction of a bicolor flex TCP semiconductor device 101 in which two types of solder resists are formed, and FIG. 7(b) is a cross-sectional view taken along line A-Axe2x80x2 in FIG. 7(a).
In the construction of the bicolor flex TCP semiconductor device 101, a driver IC chip 104 is electrically connected to a tape carrier 103 that has been formed by using a film-shaped polyimide substrate 102.
The tape carrier 103 has a copper wiring pattern that is constituted by a pair of slits 105, inner leads 106, input-side outer leads 107, output-side outer leads 108 and a test pad 109, pieces of epoxy solder resist 110, pieces of polyimide solder resist 111 and pieces of polyimide solder resist 112 that insulate and coat the slits 105 and the copper wiring pattern, and sprocket holes 113 that are used for leading and positioning the polyimide substrate 102.
In particular, on the copper wiring pattern are provided two types of solder resists, that is, the hard epoxy solder resist 110 with a young""s modulus of 380xc2x180 kgf/mm2 and the polyimide solder resist 111 having flexibility with a young""s modulus of 50xc2x120 kgf/mm2.
By utilizing its great young""s modulus, the epoxy solder resist 110 plays two roles for preventing the occurrence of bleed (flowing of solder resist mainly constituted by its solvent ingredients, after the printing process) in the polyimide solder resist 111, and for preventing the peeling of the edge of the polyimide solder resist 111 in a tin-plating formation process upon manufacturing the tape carrier 103, which will be described later. With this arrangement, the patterning precision of the polyimide solder resist 111 can be improved.
Moreover, the pieces of polyimide solder resist 112 with a young""s modulus of 50xc2x120 kgf/mm2 are formed on the undersurface (the back side of the surface on which the copper wiring pattern is formed) of the slits 105.
The driver IC chip 104 is electrically connected to the inner leads 106 through Au bumps 114, and the junctions and their adjacent portions are sealed with resin 115.
Next, referring to FIG. 8, an explanation will be given of manufacturing processes of the tape carrier 103 in the bicolor flex TCP semiconductor device 101 having the above-mentioned construction.
First, the surface of the polyimide substrate 102 (Upilex: Trademark of Ube Industries, Ltd.) is coated with a bonding agent (process 1), and a device hole, a pair of slits 105 and sprocket holes 113, etc. are formed by punching out the polyimide substrate 103 with a die (process 2).
Next, the polyimide substrate 102 is laminated with copper foil having a thickness of either 18 xcexcm, 25 xcexcm or 35 xcexcm (process 3). Moreover, pieces of polyimide solder resists 112 are formed over the pair of slits 105 from the side opposite to the surface on which the copper wiring pattern is to be formed later (process 4).
Then the copper-foil surface is coated with photoresist serving as an etching mask (process 5). Further, the photoresist is printed as a desired pattern through exposure (process 6), and developed (process 7). Here, photoresist serving as an etching mask is also formed over the device hole (process 8). Thereafter, the desired copper wiring pattern is formed by dipping the entire copper foil into a copper-foil etching liquid (process 9). After the copper wiring pattern has been formed in this manner, all of the photoresist is separated by an organic solvent or dry etching (process 10).
Next, on the surface of the polyimide substrate 102 on which the copper wiring pattern has been formed, pieces of epoxy solder resist 110 with a thickness of approximately 25 xcexcm are formed by printing at positions in which two pieces of polyimide solder resist 111, which will later be formed, are sandwiched from both sides (process 11). Thereafter, in a manner so as to cover the slits 105 serving as bending portions, pieces of polyimide solder resist 111, made of the same material as used in process 4, are formed by printing with a thickness of approximately 25 xcexcm (process 12).
Next, tin plating is applied to the surface of the exposed copper foil by the electroless plating method with a thickness of approximately 0.2 xcexcm to 0.6 xcexcm. Further, this tin plating is subjected to a curing process (heating process) so as to prevent the occurrence of whisker (process 13). Whisker refers to a needle-shaped crystal which develops in many kinds of metal when it is subjected to a stress, etc. In particular, whisker tends to develop in tin plating. When whisker develops, short circuits may be exerted between the terminals.
Lastly, the tape carrier 103, which has been manufactured through the above-mentioned processes, is shipped (process 14).
Moreover, another TCP semiconductor device, which has a construction different from the above-mentioned bicolor flex TCP semiconductor device 101, has been known. FIG. 9(a) is a plan view showing a schematic construction of a mono-color flex TCP semiconductor device 121 in which only one kind of solder resist is formed on the copper wiring pattern, and FIG. 9(b) is a cross-sectional view taken along line B-Bxe2x80x2 in FIG. 9(a).
As illustrated in FIG. 9(a) and FIG. 9(b), pieces of one kind of solder resist 123 are formed on a copper wiring pattern. The solder resist 123 is made of a hard epoxy solder resist having a young""s modulus of 200xc2x150 kgf/mm2. The mono-color flex TCP semiconductor device 121 can be produced at very low costs since the number of processes for forming solder resist is fewer than that of the bicolor flex TCP semiconductor device 101. However, because of the use of the solder resist 123 having a greater young""s modulus as described above, the mono-color flex TCP semiconductor device 121 is inferior to the bicolor flex TCP semiconductor device 101 in flexibility to bending upon assembly.
FIG. 10 shows manufacturing processes of a tape carrier 122 in the mono-color flex TCP 121. The manufacturing processes are different from those of the tape carrier 103 in the bicolor flex TCP semiconductor device 101 in that, as described above, only one kind of the hard epoxy solder resist 123 having a young""s modulus of 200xc2x150 kgf/mm2 is formed on the copper wiring pattern, and the other processes are carried out in the same manner as described above; therefore, the description thereof is omitted.
Next, referring to FIG. 12(a), an explanation will be given of a packaging method of the bicolor flex TCP semiconductor devices 101 onto a liquid crystal panel 201 and a PWB (Printed Wiring Board) 202. In general, for example, in the case of a liquid crystal panel of the 12.1-inch size having 1024 dotsxc3x97768 dots, upon packaging the bicolor flex TCP semiconductor devices onto the liquid crystal panel, approximately thirteen bicolor flex TCP semiconductor devices are mounted on the source side of the frame edge on one side in the liquid crystal panel 201 as drivers.
First, an ACF (Anisotropic Conductive Film), which is an anisotropic conductive bonding agent, is temporarily press-bonded onto the liquid crystal panel 201. The ACF, which has some kinds in width ranging from 1.2 mm to 3 mm, is properly selected so as to fit the size of the frame edge of the liquid crystal panel 201. Therefore, for example, if the width of the frame edge is narrow, an ACF with a narrow width is selected. Upon temporarily press-bonding the ACF, while the ACF is being affixed onto the liquid crystal panel 201, a tool, heated to 90xc2x0 C., is pressed thereon for approximately 2 seconds. At this time, the ACF reacts due to the heat and is cured, but is not completely cured so that an actual press-bonding process can be carried out later.
Upon completion of the temporary press-bonding process of the ACF, spacers, which have adhered to the ACF, are separated, and outer leads 108 on the output side of the bicolor flex TCP semiconductor devices 101 are temporarily press-bonded thereto. In this case, the bicolor flex TCP semiconductor devices 101 and the liquid crystal panel 201 are positioned by using alignment marks that have been respectively formed thereon. Prior to this temporary press-bonding process, the bicolor flex TCP semiconductor devices 101, which are connected in a reel shape, are punched out into respective pieces by using a die. Then upon temporarily press-bonding, a tool, heated to 100xc2x0 C., is pressed thereon with a load of 10 kgf/cm2 for 3 seconds; however, the ACF is not completely cured.
After the temporary press-bonding process of the bicolor flex TCP semiconductor devices 101, an actual press-bonding process is carried out. In the actual press-bonding process, a tool, heated to 200xc2x0 C., is pressed with a load of 35 kgf/cm2 for 20 seconds onto all the bicolor flex TCP semiconductor devices 101 which have been temporarily press-bonded to the liquid crystal panel 201, at one time.
After the bicolor flex TCP semiconductor devices 101 have been packaged onto the liquid crystal panel 201, outer leads 107 on the input side of the bicolor flex TCP semiconductor devices 101 are joined to the PWB 202. With respect to the packaging method of the bicolor flex TCP semiconductor devices 101 onto the PWB 202, a soldering method and a method using an ACF are applied. In the packaging method by using the ACF, all the bicolor flex TCP semiconductor devices 101 are packaged at one time onto the PWB 202 which has been aligned. At this time, a thermal stress, exerted due to a difference in coefficient of thermal expansion between the PWB 202 and a glass substrate constituting the liquid crystal panel 201, is concentrated on the bicolor flex TOP semiconductor devices 101.
The bicolor flex TCP semiconductor devices 101 have to be bent with the thermal stress being applied thereon so that the PWB 202 is placed on the back side of the liquid crystal panel 201. Consequently, the stress is further concentrated on the copper wiring pattern of the flex TCP semiconductor devices 101. In particular, the thermal stress increases as the liquid crystal panel 201 becomes larger.
Moreover, there is another method in which a straight TCP semiconductor device 121 without slits, as illustrated in FIG. 11, is packaged without being bent as illustrated in FIG. 12(b). In this method, however, unlike the bicolor flex TCP semiconductor device 101, it is not possible to minimize the frame-edge size of the liquid crystal panel 201. Therefore, this packaging method has a disadvantage in the case when a liquid crystal panel, which is as large as possible, is installed inside an apparatus having a limited space, such as a notebook PC.
Next, referring to FIGS. 13(a) and 13(b), an explanation will be given of a testing method for disconnection in the copper wiring pattern of the flex TCP semiconductor device 101. Conventionally, a TEG (Test Element Group) 131 serving as a testing pattern, as illustrated in FIG. 13(a), was manufactured, and the TEG 131 was bent through the MIT (Massachusetts Institute of Technology) method as shown in FIG. 13(b) so as to test the copper wiring pattern 132 for disconnection.
The following description will discuss one example of this testing method. A weight of 100 g was mounted on the TEG 131 that was pinched by jigs 135 at both sides thereof, and the portion of a slit 133 having a width of 1 mm was bent to 0xc2x0 via 90xc2x0 with a bending radius of 0.3 mm to 0.4 mm, and further bent so as to return to 180xc2x0. When it was bent from 0xc2x0 to 180xc2x0, this was counted as one bending process. These processes were repeated until disconnection had occurred in the copper wiring pattern 132 formed on the slit 133, and the number of bending processes up to the disconnection was calculated. The greater the number of the bending processes up to the disconnection, the better the resistance to bending was considered to be. The resistance varied depending on the solder resist 134 used as the TEG 131, and conventionally, solder resist 134, which did not suffer disconnection even under the MIT tests of 20 times, was conventionally used.
However, in the bicolor flex TCP semiconductor device 101 using two types of solder resist as shown in FIG. 7, solder resist having a great young""s modulus is adopted. For this reason, when the bicolor flex TCP semiconductor devices 101 are packaged on a large-size liquid crystal panel of not less than 17 inches, the stress onto the bicolor flex TCP semiconductor devices 101, exerted due to a difference in coefficient of thermal expansion between the liquid crystal panel 201 and the PWB 202, increases, and is concentrated on the copper wiring pattern, making the copper wiring pattern susceptible to disconnection.
In this case, the portion that is most likely to have disconnection is in the vicinity of the outer leads 108 on the output side at which the liquid crystal panel 201 and the bicolor flex TCP semiconductor devices 101 are joined by the ACF, as illustrated in FIG. 13. The larger the size of the liquid crystal panel 201, the more conspicuous the occurrence of disconnection becomes, raising a serious problem in production of the liquid crystal display device.
Moreover, in the bicolor flex TCP semiconductor device 101, the patterning precision of the pieces of epoxy solder resist 110, first formed, is xc2x10.2 mm, and the patterning precision of the pieces of polyimide solder resist 111, formed thereafter, is xc2x10.3 mm. Therefore, at portions in which the two types of solder resist contact, the patterning precision becomes xc2x10.5 mm, which is a comparatively bad value.
Furthermore, in the bicolor flex TCP semiconductor device 101, since the hard epoxy solder resist 110 is used, the bicolor flex TCP semiconductor device 101 itself becomes harder, thereby losing its flexibility. In addition, when hard solder resist is formed on the bicolor flex TCP semiconductor device 101, warping occurs in the bicolor flex TCP semiconductor device 101, failing to smoothly transport the bicolor flex TCP semiconductor device 101 in the assembling process. The warping is more likely to occur in particular when the width of the bicolor flex TCP semiconductor device 101 exceeds 48 mm.
Furthermore, in the bicolor flex TCP semiconductor device 101, since two types of solder resist are formed, two dedicated printing machines for printing these two types are required, and the management of solder resist becomes more complicated. The resulting problem is an increase in the production cost of the tape carrier 103.
In contrast, when only polyimide solder resist is formed as the solder resist, two problems, that is, warping of the flex TCP semiconductor device and an increase in the production cost of the tape carrier, can be solved. However, since polyimide solder resist has a low thixotropy, bleeding 142 occurs on the pattern edge 141 as shown in FIG. 14. Thixotropy refers to a scale for estimating the property of a substance in which stirring causes a reduction in viscosity while standing causes an increase in viscosity is estimated. For example, when the thixotropy of the solder resist is high, the patterning precision becomes better upon printing because of a reduction in viscosity, and the occurrence of bleeding is reduced after printing because of an increase in viscosity. Here, FIG. 14 is an enlarged view in which one portion of the upper surface of a TCP semiconductor device suffering bleeding 142 is shown in an enlarged manner.
Therefore, when the thixotropy is low, the pattern edge 141 of the solder resist 143 is not printed accurately, resulting in failure to properly manufacture the tape carrier. Moreover, solder resist 143 flows to reach the inner leads 144 inside the device holes of the tape carrier, resulting in a problem in which no bonding is available during an ILD (Inner Lead Bonding) process.
Moreover, another problem with the conventional bicolor flex TCP semiconductor device 101 is that pieces of polyimide solder resist 112, formed on the back side of the slits 105, have their pattern edge separated during the tin plating process and that the separated solder resist causes dusts, thereby contaminating the tape carrier 103.
Furthermore, in the flex TCP semiconductor device in which only polyimide solder resist is used as the solder resist, during the process for sealing the inner leads with resin, since the polyimide solder resist merely has a low adhering property to liquid epoxy resin, it becomes difficult to manufacture the flex TCP semiconductor device.
In addition to the above-mentioned problems, the MIT testing method for testing disconnection of the copper wiring pattern of the flex TCP semiconductor device 101 also has the following problem: In the MIT test, although disconnected portions, which are to be tested, are located in the vicinity of the edge of the slit 133 as shown in FIG. 13(b), these portions are different from actual disconnected portions that occur upon being bent after the flex TCP semiconductor devices 101 have been packaged on the liquid crystal panel 201 and the PWB 202. The disconnected portions occurring due to the bending after the packaging are located in the vicinity of the edges of portions at which the flex TCP semiconductor devices 101 are joined to the liquid crystal panel 201 as shown in FIG. 15.
Moreover, as the size of the liquid crystal panel becomes larger, the stress to the flex TCP semiconductor devices 101, which is exerted due to a difference in coefficient of thermal expansion between the liquid crystal panel 201 and the PWB 202, increases, and the stress is concentrated on the copper wiring pattern, making it more susceptible to disconnection. For example, although defects due to disconnection seldom occur in the case of the liquid crystal panel of 10.4 inches, they become conspicuous in the case of the large-size liquid crystal panel exceeding 11.3 inches.
In other words, although the MIT test can detect failure due to disconnection in the slit 133, it fails to properly evaluate the resistance to bending of the flex TCP semiconductor devices 101 upon packaging. Therefore, for example, even when, in the MIT test, a better result is obtained in flex TCP semiconductor devices using one type of epoxy solder resist than in flex TCP semiconductor devices using two types of solder resist, it sometimes happens in an actual packaging process on a liquid crystal panel that those device using one type of epoxy solder resist are more susceptible to disconnection.
As described above, in the conventional disconnection-testing method, it is not possible to determine a manufacturing method for flex TCP semiconductor devices which would be suitable for large-size liquid crystal panels. Moreover, even if the evaluation is made by actually packaging the flex TCP semiconductor devices on a liquid crystal panel, the possibility of occurrence of defects due to disconnection in the liquid crystal panel packaging process is normally in the order of PPM, that is, very low, failing to allow rational evaluation in a short period. Therefore, it is not possible to easily find a method for producing large-size liquid crystal displays exceeding 15 inches, which are more likely to have defects due to disconnection, with high yield.
The objective of the present invention is to provide a tape carrier package semiconductor device which is highly flexible and less susceptible to disconnection in the metal wiring pattern upon packaging, a liquid crystal display using such a device, and a disconnection-testing method for such a device.
In order to achieve the above-mentioned objective, the tape carrier packaging semiconductor device of the present invention, which has a tape carrier and semiconductor devices that have been packaged on the tape carrier, is characterized in that the tape carrier is provided with an insulating tape, a metal wiring pattern installed on one surface of the insulating tape, a through hole that is provided in a manner so as to penetrate the insulating tape so that the insulating tape is allowed to bend, a first insulating protective film for insulating and covering the metal wiring pattern and the through hole on the metal-wiring-pattern side, and a second insulating protective film for insulating and covering the through hole on the side opposite to the metal-wiring-pattern side, and also characterized in that the first and second insulating protective films are made of solder resist whose young""s modulus is in the range of 5 kgf/mm2 to 70 kgf/mm2.
With the above-mentioned construction, since the young""s modulus is set in the range of 5 kgf/mm2 to 70 kgf/mm2, the solder resist functions as a very flexible insulating protective film.
Therefore, for example, even if the tape carrier package semiconductor devices are packaged on a liquid crystal panel, the metal wiring pattern is hardly susceptible to disconnection. Further, the occurrence of warping in the tape carrier package semiconductor devices is reduced, and the manufacturing cost of the tape carrier can be reduced.
Moreover, the liquid crystal panel display of the present invention, which is provided with a tape carrier package semiconductor device having a tape carrier and semiconductor devices for driving a liquid crystal panel that are installed on the tape carrier and the liquid crystal panel, is characterized in that the tape carrier is provided with an insulating tape, a metal wiring pattern installed on one surface of the insulating tape, a through hole that is provided in a manner so as to penetrate the insulating tape so that the insulating tape is allowed to bend, a first insulating protective film for insulating and covering the metal wiring pattern and the through hole on the metal-wiring-pattern side, and a second insulating protective film for insulating and covering the through hole on the side opposite to the metal-wiring-pattern side, and also characterized in that the first and second insulating protective films are made of solder resist whose young""s modulus is in the range of 5 kgf/mm2 to 70 kgf/mm2.
With the above-mentioned construction, since the first and second insulating protective layers are made of solder resist whose young""s modulus is set in the range of 5 kgf/mm2 to 70 kgf/mm2, the liquid crystal display is allowed to have a tape carrier package semiconductor device with high flexibility.
Therefore, for example, even if the tape carrier package semiconductor devices are packaged on a liquid crystal panel display, the metal wiring pattern is not susceptible to disconnection. Further, the warping in the tape carrier package semiconductor devices is suppressed, and the manufacturing yield of the liquid crystal panel display can be improved.
Moreover, the testing method for disconnection of the present invention, which is a testing method for disconnection in a tape carrier which constitutes a tape carrier package semiconductor device and in which a metal wiring pattern and an insulating protective film for insulating and coating the metal wiring pattern are placed on an insulating tape, is characterized by the steps of: manufacturing a testing tape carrier having a construction identical to the tape carrier; connecting both of the ends of the testing tape carrier to plate-shaped substrates; aligning the substrates face to face with each other so that the testing tape carrier is brought into a bent state; and exposing the testing tape carrier to temperature environments which change with a predetermined cycle so as to count the number of cycles until the metal wiring pattern in the testing tape carrier has been disconnected.
In the above mentioned method that is a testing method for disconnection in the metal wiring pattern of a tape carrier constituting a tape carrier package semiconductor device, a testing tape carrier having a construction identical to the tape carrier is manufactured, and this is brought into a bent state with the liquid crystal panel and the circuit board being aligned face to face with each other, and in this state, the testing tape carrier is exposed to temperature environments which change with a predetermined cycle so as to find the number of cycles until it has been disconnected.
By bringing the testing tape carrier into the above-mentioned bent state, it becomes possible to create a state close to the state in which the tape carrier package semiconductor device is actually packaged on a liquid crystal panel. When the testing tape carrier is exposed to the temperature environments which change with a predetermined cycle in this state, possible disconnected portions coincide with disconnected portions occurring in an actual liquid crystal panel packaging process, and the occurrence of the possible disconnected portions is accelerated.
Therefore, by carrying out the above-mentioned test for disconnection, it becomes possible to positively confirm defects due to disconnection occurring in the liquid crystal panel packaging process of the tape carrier package semiconductor device in a short time.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.